An investigation into the microstructure and weldability of a tantalum-containing cast cobalt-based superalloy

Montazeri, Mojtaba; Ghaini, F. Malek; Farnia, Amirreza

doi:10.3139/146.110616

Cited by 6 publications

(3 citation statements)

References 12 publications

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“…These carbides are not stable at high temperature and they tend to partially, and sometimes totally, dissolve at temperatures as high as 1100°C. This phenomenon is also encountered in cobalt-based superalloys in which MC carbides, notably tantalum carbides (TaC) [31][32][33][34], are more stable. Furthermore, these TaC carbides obtained in cobalt-based superalloys present a script-like morphology issued from their eutectic solidification with matrix.…”

Section: Introductionmentioning

confidence: 98%

Creep and oxidation kinetics at 1100°C of nickel-base alloys reinforced by hafnium carbides

Berthod

Conrath

2016

Materials & Design

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The mechanical reinforcement of polycrystalline alloys at elevated temperature may be achieved by HfC carbides. Generally such alloys must be also resistant against oxidation by hot gases and corrosion by molten substances. Polycrystalline chromium-rich nickel-based alloys represent a good solution for answering these requirements about the high temperature chemical resistance. Unfortunately they tend to be rather mechanically weak at high temperature compared to γ/γ' single crystals. In this work a new family of alloys, combining a chromium-rich nickel-based matrix and an interdendritic HfC carbide network, is studied. Two equiaxed cast alloys were elaborated by classical foundry and the obtained microstructures were examined. Two types of high temperature properties were characterized at 1100°C, creep resistance and oxidation kinetic. The microstructures of the two alloys are composed of a dendritic austenitic matrix and of script-like eutectic carbides which are recognized to be very favorable for high strength at high temperature. Creep tests proved this potential benefit by showing that these alloys are much more resistant than usual cast polycrystalline nickel-based alloys. The base made of nickel and the 25 wt.% content in chromium allow obtaining a chromia-forming behavior leading to good resistance against oxidation in hot air.

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Section: Introductionmentioning

confidence: 98%

Creep and oxidation kinetics at 1100°C of nickel-base alloys reinforced by hafnium carbides

Berthod

Conrath

2016

Materials & Design

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“…Often, the resultant microstructures in fusion-based welded joints must be modified in order to improve the part mechanical properties. These microstructural modifications are often performed by post-weld heat treatments, which can induce dissolution or formation of new phases/precipitates or promote stress relieving [78][79][80][81].…”

Section: Cocrfenimn Hea Systemmentioning

confidence: 99%

A Short Review on Welding and Joining of High Entropy Alloys

Lopes

Oliveira

2020

Metals

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High entropy alloys are one of the most exciting developments conceived in the materials science field in the last years. These novel advanced engineering alloys exhibit a unique set of properties, which include, among others, good mechanical performance under severe conditions in a wide temperature range and high microstructural stability over long time periods. Owing to the remarkable properties of these alloys, they can become expedite solutions for multiple structural and functional applications. Nevertheless, like any other key engineering alloy, their capacity to be welded, and thus become a permanent feature of a component or structure, is a fundamental issue that needs to be addressed to further expand these alloys’ potential applications. In fact, welding of high entropy alloys has attracted some interest recently. Therefore, it is important to compile the available knowledge on the current state of the art on this topic in order to establish a starting point for the further development of these alloys. In this article, an effort is made to acquire a comprehensive knowledge on the overall progress on welding of different high entropy alloy systems through a systematic review of both fusion-based and solid-state welding techniques. From the current literature review, it can be perceived that welding of high entropy alloys is currently gaining more interest. Several high entropy alloy systems have already been successfully welded. However, most research works focus on the well-known CoCrFeMnNi. For this specific system, both fusion and solid-state welding have been used, with no significant degradation of the joints’ mechanical properties. Among the different welding techniques already employed, laser welding is predominant, potentially due to the small size of its heat source. Overall, welding of high entropy alloys is still in its infancy, though good perspectives are foreseen for the use of welded joints based on these materials in structural applications.

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“…They lead to {matrix & carbides} eutectics which are 40°C more refractory [14,15]. They are also more stable at high temperature [16,17], even if long stay at elevated temperature may induce TaC degradation [16,18] with possible deleterious consequences on high temperature properties [19,20]. Beside new metallurgical ways for cobalt-based superalloys such as single-crystal solidification [21], γ/γ' Co-based alloys [22] or Co-based superalloys strengthened by highly temperature-resistant HfC carbides [23,24], the principle of reinforcement by script-like eutectic TaC carbides is still of interest, as rather recently demonstrated for some industrial applications (e.g.…”

Section: Introductionmentioning

confidence: 99%

Improvement of the high temperature oxidation of TaC-strengthened Co(Cr)-based cast superalloys by the addition of nickel

Berthod

Gomis

2019

Corrosion Engineering, Science and Technology

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In this work, nickel is added in substitution to cobalt in the composition of a cast cobalt-based chromium-rich superalloy designed to obtain a double-phased {fcc matrix + TaC} microstructure. Two nickel amounts were tested, 13 and 26 wt-%Ni, for 25 wt-%Cr, 0.4 wt-%C and 6 wt-%Ta, the rest being cobalt. The obtained as-cast microstructures are not different from the starting alloy's one, contrarily to the hardness which became lower. The oxidation tests at 1200°C for 170 h demonstrated a significant improvement of the alloy's behaviour, especially for an addition of 26 wt-%Ni. This seems to be attributed to an easier Cr diffusion towards the oxidation front as suggested by the observed Cr contents in extreme surface as well as by the lower Cr concentration gradients. In addition, the TaC seemed to be morphologically more stable in the presence of nickel in the alloys than in the absence of Ni.

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An investigation into the microstructure and weldability of a tantalum-containing cast cobalt-based superalloy

Cited by 6 publications

References 12 publications

Creep and oxidation kinetics at 1100°C of nickel-base alloys reinforced by hafnium carbides

Creep and oxidation kinetics at 1100°C of nickel-base alloys reinforced by hafnium carbides

A Short Review on Welding and Joining of High Entropy Alloys

Improvement of the high temperature oxidation of TaC-strengthened Co(Cr)-based cast superalloys by the addition of nickel

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